One of the challenges of image-guided medical, in particular surgical, procedures is to efficiently use the information provided by the many imaging techniques the patient may have been through before and during the intervention.
For example, in cardiology, physicians often have access to real-time X-ray images acquired by a C-arm. These images have a very good spatial and temporal accuracy thus enabling to follow precisely the progression of even thin catheters and other interventional tools. However, soft-tissues are barely visible in these images, and furthermore, these images are projections which do not give a direct access to the volumetric geometry of the intervention scene. To gain access to this important information also, a solution consists in using a second imaging modality which is both 3D and able to image soft-tissues.
One possible choice for this second imaging system is 3D ultrasound imaging. The advantage of this modality is that it can be used in real-time during the surgical procedure. In cardiological procedure, trans-esophageal probes can be navigated right next to the heart, producing real-time volumetric images with anatomical details that are hardly visible with standard transthoracic ultrasound.
A typical intervention is percutaneous valve repair (PVR) such as mitral clipping where the simultaneous involvement of X-ray and ultrasound has been found helpful to monitor the placement of the tool/endoprosthesis with respect to the soft-tissue anatomy.
It has been found however that the the usual way of displaying both ultrasound and X-ray real-time streams, such as in Applicant's US WO 2011/070492, are at times not intuitive enough for the operator to readily understand the spatial relationship between the two modalities when carrying out the intervention, oftentimes under great stress.